In 2010, Mr. Nader and his colleagues at California State University, Chico, published a review in Nutrition Journal that found that on a gram-for-gram basis, grass-fed beef contained higher levels of beneficial fats such as omega-3 fatty acids and conjugated linoleic acid, or C.L.A. It also contained more antioxidants and higher levels of beta carotene, a precursor to vitamin A that can give grass-fed beef a yellowish appearance.

“When people go to their retail store and see yellow fat, they think there’s something wrong with it,” Mr. Nader said. “That’s not some bad piece of meat. That’s actually vitamin A you’re looking at.”